It's amazing how long people can go believing a 'fun fact' they heard once, without ever actually looking into it. My parents used to tell me that drinking soda would stunt my growth, and I thought, "Oh sh*t, okay, thanks for the heads-up," and then proceeded to avoid soda at all costs and silently judge anyone who dared take a sip. It wasn't until I was much older, and had already completely stopped growing vertically, that I realized this was straight-up BS. Though this is what parents do, lying is easier than explaining.
If you've ever come across someone with a lot of questionable 'knowledge,' you'll probably enjoy this Reddit thread.